There currently exists various types of panel antenna, such as a reversed L-type of or a reversed F-type of antenna which are small and suitable for incorporation into portable equipment as an antenna for radio communication equipment, for instance, radio equipment and a transceiver each mounted on a vehicle, a cordless telephone set, mobile radio equipment, or portable radio equipment each of which is growing in use for a general purpose.
As improvement in the panel antennas, there has been disclosed configuration of an antenna for radio communication equipment, in Japanese Patent Publication No. HEI 2-55961. The antenna can easily match impedances, in other words, has high-flexibility in adjustment of antenna-impedance, and is well suited for size reduction even if a geometrical dimension of a main component of the antenna and a position for taking out a feeding point are restricted.
FIG. 7 schematically shows the configuration of the conventional type of antenna applied to a cordless telephone set. In FIG. 7, the antenna in the example comprises a conductive main erecting surface section 711 with one edge thereof connected to a shield housing 730 which is a ground conductor and erecting to the other edge thereof by a height H; a conductive main horizontal surface section 712 having a width W with one edge thereof connected to the other edge of the main erecting surface section 711, crossing the main erecting surface 711 at right angles and horizontally extending to the other edge thereof by a length H; a conductive auxiliary erecting linear section 713 with one edge thereof connected to the shield housing 730 via a feeding point 720, and linearly extending to the other edge thereof in parallel to the main horizontal surface section 712; a conductive auxiliary horizontal linear section 714 with one edge thereof connected to the other edge of the auxiliary erecting linear section 713, said conductive auxiliary horizontal linear section linearly extending, at a specified space to the main horizontal surface section 712, to the other edge thereof in parallel to the main horizontal surface section 712; a linking section 715 for electrically connecting the other edge of the auxiliary horizontal linear section 714 to a position of the other edge of the main horizontal surface section 712 or a position at a specified space from the position of the other edge thereof; a first conductor width section 716 having a width t1 provided along the whole length or a portion of the length of the auxiliary horizontal linear section 714 and constituting a capacitor for adjusting impedance; and a second conductor width section 717 having a width t2 provided along a portion of the length of the auxiliary horizontal linear section 714 and constituting a capacitor for adjusting a central frequency.
In the antenna based on the conventional technology described above, impedance can be adjusted by (1) adjusting a distance between the auxiliary horizontal linear section 714 and the main horizontal surface section 712, (2) adjusting a position at which the auxiliary horizontal linear section 714 is connected to the main horizontal surface section 712 via the linking section 715, (3) adjusting a capacity according to a width t1 and a length of the first conductor width section 716, and (4) adjusting a position of forming the second conductor width section 717 according to change in a longitudinal direction of the auxiliary horizontal liner section 714.
Also, in a case where the second conductor width section 717 is provided right under the other edge of the main horizontal surface section 712 in which a voltage value becomes a maximum, central frequency in a resonance system of the antenna can be adjusted according to adjustment of the width t2 and a dimension of the area.
In the conventional type of antenna for radio communication equipment as described above, a main erecting surface section and a ground conductor each connected to a feeding point comprise a shield housing for shielding circuit components mounted on a printed board, so that restriction is added to the design that the upper edge surface portion of the shield housing facing to the main horizontal surface section should be formed in parallel to the main horizontal surface section, which lowers the flexibility of the designing, and it is difficult to uniformly form a ground potential surface facing to the main horizontal surface section and in parallel thereto.
Also, the auxiliary erecting linear section, auxiliary horizontal linear section, linking section, first conductor width section, and second conductor width section each one of an antenna for radio communication equipment are formed on the printed board, so that, in designing an antenna as well as a printed board design, designing restrictions are added to each design, and for this reason, design flexibility as a whole radio communication equipment is lowered.
Accordingly, the invention is made to solve the above-described problems and it is an object of the present invention to provide an antenna for radio communication equipment which has high designing flexibility and is excellent in manufacturing workability because only an antenna therein can be designed independently from the other components by forming a ground potential surface in substantially parallel to the main horizontal surface section monolithically formed with the antenna.
Also, it is another object of the present invention to provide an antenna for radio communication equipment which can flexibly be designed because the antenna has high flexibility in adjustment of an impedance and a central frequency in a resonance system of the antenna even if dimensions of the antenna are under certain restrictions.
Further, it is another further object of the present invention to provide an antenna for radio communication equipment in which components each constituting the antenna are monolithically formed, and an antenna can be designed separately from other portions of the radio communication equipment, so that high flexibility in designing can be achieved as a whole radio communication equipment.